The MFB Center coordinates and initiates comparative toxicological and pharmacological research on an organ system level. Many toxicants reach man through the aquatic food chain and with the growing importance of food from the sea, this food chain can provide a sensitive indicator of organ toxicity to man as well as an indicator of accumulation of toxicant. With the very large variety of species, aquatic organisms can be selected for models to study the effect of toxicants on man. Specifically, comparative studies are conducted on organ function and operation, including influence of organ operation by physical and chemical factors in the environment. Research concerning organ function, the normal action of the organ, is necessary for comparisons between aquatic animals and man. Organ operation, the processes involved within the organ's function, is then assessed with regard to the impact of environmental changes. These changes are studied with regard to understanding how they may be extrapolated for man. The MFB Center functions to coordinate and focus the research to assure meaningful comparative studies of understanding how the toxicant might affect man. The action of environmental factors on organ operation is being investigated at several levels, such as effects on transport of material in and out of the organ, metabolic changes and alterations as influenced by hypoplasia, hyperplasia, or neoplasia. Alterations of mechanisms of action resulting from environmental exposure in aquatic animals is being studied and compared with analogous changes in mammals, particularly man.